Laser (Light Amplification by Stimulated Emission of Radiation), invented almost sixty year ago, has found its applications in a wide variety of different areas, such as scientific research, medical application, military, industrial and commercial and people's everyday life. It has been used in spectroscopy, ranging and sensing devices, microscope, bar code reading, targeting, cosmetic surgery, cutting, welding, computer mouse and so on.
In these applications, different types of laser have been generated through different approaches, by different apparatuses. Up to date, laser comprises the following major types, gas lasers, solid state lasers, metal vapor laser, semiconductor laser and so on. Among these laser types, laser diode is not just the main family of semiconductor laser, but also, in quantity, the most common one among any types of laser currently available. The laser diode has found wide applications in many industrial areas and people's everyday life. In telecommunication, as it is easily modulated and easily coupled light sources for fiber optics communication. It is used in various measuring instruments, such as rangefinders. Other common uses include barcode readers, scanning and laser printer, as well as night light and emergency light. Most of them are common products in people's daily life. In comparison to other types of laser, the low cost of mass-produced diode lasers makes them essential for those mass-market applications. Today laser diodes are available with power outputs ranging from a few milliwatts, like those found in laser pointers, to laser diodes emitting many watts of optical energy and are used to cut through solid metal and in high energy physics experiments.
In most of the applications, the laser is not used in a standing alone manner. Instead, it is always mounted to some adaptors or connectors that further link the laser diode to the devices that are using it. In most of the cases, the mounting adaptor is a heat sink that helps to dissipate the heat generated from the laser diode. Albeit itself does not generate any laser, the heat sink mount is actually critical for a laser diode's function. It significantly influences many key aspects of a laser diode. Laser diode is a semiconductor, which can only functions appropriately within a very narrow temperature range. Heat dissipation is thus always a key issue for any semiconductor and device containing semiconductor in it, such as a computer. Without efficient heat dissipation, the heat generated will make a semiconductor component, as well as the entire device, quickly fail. In this regard, a heat sink is the key for a laser diode's properly functioning and its reliability.
In addition, a heat sink mount is particularly important for a laser diode. That's because a laser diode is not a normal semiconductor, but a specific semiconductor that can generate laser. In this concern, like many other types of laser generating devices, it comprises a mirror or reflecting plane as a basic component. In a laser diode, this has been achieved by cleaving the semiconductor wafer to form a spectacularly reflecting plane. It is the easiest way to make such a micro reflecting device within a semiconductor. However, the atomic states at the cleavage plane have actually been altered. As a result, when the generated laser light is propagated via this cleavage plane to the outside of the semiconductor crystal structure, a portion of the light will be absorbed by the surface state of this cleavage plane and via the interaction between the photon and electron, it will be eventually converted into heat. In light of the foregoing, the proper function of such heat sink is particularly important. If it can not quickly and efficiently transfer such heat to outside, the entire laser diode will fail soon.
What's even worse, in the foregoing scenario, if the heat can not be quickly dissipated via its heat sink mount, the accumulated heat will heat the cleavage plane to a higher temperature, which further leads to shrink of the bandbag in the cleavage area, such shrink functions to align the electronic transition and the photon energy; as a result, such alignment leads to more absorption. Clearly, this is a positive feedback loop. Eventually, in a worse scenario, the entire cleavage surface would be melt down; and thus the whole laser diode has to be scrapped.
In addition to the aforementioned issues, the function of a laser diode is highly correlated to its temperature, too. In general, the wavelength of generated laser typically would alter by 0.9 nm for every 3.0 degrees Celsius. On the other hand, as the temperature of a laser diode increases, the optical power output will drop.
Accordingly, a heat sink is truly critical for a laser diode's proper function and its reliability. In order to remove as much heat as possible from a laser diode, the contact between the heat mount and the laser diode is the key. It needs to match a laser diode's shape and perfectly contact the surface of the laser diode. The larger the contact area, the better the heat dissipation effect is. It also needs to avoid any air within the heat sink, between the heat sink and the laser diode, as air is one of the poorest among the common materials for heat transfer. Accordingly, any air staying in between the heat sink mount and the laser diode would compromise the heat dissipation effect.
In order to achieve the best heat dissipation effect from a heat sink mount, the contact surface of the laser diode and the heat sink mount needs to be optimized; besides, the fastening means between different components of the heat sink is also very important. If glue has been used for such purpose, it should be make sure that such glue functions properly at a high temperature, as the heat sink mount could be pretty hot after absorbing heat energy from the laser diode. On the other hand, it should also be make sure that such glue not evaporates any toxic substance at a high temperature, since the laser diode are applied in many devices in people's everyday life, or even used directly on human body, such as in a cosmetic or dental surgery. In addition, it has to be careful with glue as glue may act as insulation and thus compromise the heat sinking ability.
Furthermore, as mentioned above, the heat sink mount and the laser diode are always made into an assembled one piece in the device, for the purpose of heat dissipation, as well as mechanical protection and connection of the tiny laser diode. So, in a sense, the laser diode and its heat sink mount would be treated as one piece. Considering its specific structural design, manufacturing equipments and raw materials used for manufacture, the costs for manufacturing the laser diode part do not have a large room for price drop currently. However, due to its relatively simple structure and commonly used raw material, the costs from the part of heat sink mount can actually be further reduced. In fact, a significant part of such cost is derived from assembling the heat sink pieces together, as well as mounting a laser diode into the heat sink. Through redesign the heat sink components, assistant assembling tools, and streamlining the assembling process, the assembly cost could be reduced and the production efficiency could be improved, which would reduce labor costs to increase production rate per day.
It is therefore an objective of the present invention to provide a new type of heat sink mount for laser diode. Such heat sink mount is easy to assemble, of a low defective rate and at the same time, provide a better heat dissipation effects.